The present invention relates to a rotary drive and in particular to a rotary drive suitable for use with rotary valve mechanisms in which a intermittent drive is desirable.
It has been proposed hitherto to use rotary valves for internal combustion engines, but in order to seal the rotating valve member on the high pressure (i.e. compression and combustion) strokes of the engine, complex gas seals have been required. Furthermore, such systems result in high frictional loads with consequent reduction in efficiency and high wear rates. In order to reduce the problems of high frictional loads, it has been proposed to reduce the speed of rotation of the valves on the high pressure strokes of the engine, using a differential drive gear arrangement. Such systems are however relatively complex and the space required for the differential drive gear arrangement will substantially increase the overall height of the engine.
The present invention provides a rotary drive of relatively simple construction, which will significantly reduce the speed of rotation of a rotary valve during high pressure strokes of the engine.